The objective of this project is to build a liquid-xenon multi-wire gamma-ray camera, and to clinically evaluate its performance in nuclear medicine applications using radioactive pharmaceuticals for the diagnosis of various diseases in human subjects. Compared with other techniques, the liquid-xenon camera offers an unprecedented combination of gamma-ray detection efficiency, positional accuracy, and potential for upscaling. The basic detector of the camera (under construction) consists of a volume of liquid xenon, 2.0 cm thick, containing 83 anode wires and 63 cathode strips, each set orthogonal to the other. The useful field of the camera will be approximately 20 cm X 16 cm. It will have an inherent resolution of 2.5 mm FWHW and the energy resolution and efficiency will be similar to NaI (TI). The readout uses a preamplifier for each anode and cathode line and digital electronics to calculate the orthogonal coordinates (X and Y). Pulse height selection will be used to discriminate against gamma-rays that scatter in the patient, and the X and Y signals can be collected at an average rate of 3 X 10 to the 5th power counts per second using a digital computer system presently available. The small 6 cm X 6 cm camera and readout was completed and successfully operated with support from the previous year's grant. Improvements in reliability, energy discrimination, and signal-to-noise have been achieved using a dual-phase approach. In this mode, gamma- rays are converted with high efficiency in a layer of liquid xenon and the associated ionization electrons are pulled into a gaseous phase where they are proportionally amplified. High resolution imaging in nuclear medicine is limited by the poor transmission of collimators. Thus, theory and construction of optimal collimators is an integral part of this proposal. We have designed and constructed high resolution collimators for 141 keV and propose to build a low leakage collimator for 511 keV that is vibrated during imaging. This imaging technique promises to overcome basic limitations for present gamma cameras speed and inherent resolution - and increase the useful energy range to cover the span from 40 keV to 1 MeV.